Use of wood ash and paper sludge as potting substrate and potential soil amendment for agriculture production on podzols in boreal climate

Abstract

This study was designed to investigate the use of wood ash (WA), paper sludge (PS) (wastes from paper mill) and biochar (BC) as potting substrates, and potential amendment for podzolic soil. WA and PS were applied by two methods; 1) on volume basis to prepare a suitable potting media (Study-one), and 2) on mass basis to amend the podzolic soil and for assessment of heavy metals leaching behavior (Study-two). Important physicochemical properties were measured in both experiments. In study one, the treatment of 50% PS + 25% BC was noted as the best treatment based on the measured properties as a suitable potential potting media. This treatment had high organic matter (8.33%), field capacity–FC (0.33 cm³ cm⁻³) and plant available water-PAW (0.40 cm³ cm⁻³) with low bulk density (0.53 g cm⁻³). In the study-two, WA alone and with BC did not show significant difference from control to improve the physicochemical properties of amended soil, and PS with combination of BC found as the best treatment having optimum pH (6.5) with the highest total porosity (0.68 cm³ cm⁻³), FC (0.36 cm³ cm⁻³) and PAW (0.28 cm³ cm⁻³) among all treatments. BC addition in leaching column experiment significantly reduced the heavy metals (Arsenic, Cadmium, Cobalt, Copper, Molybdenum and Nickel) concentrations in collected leachates compared to bC unamended treatments. Outcomes of these studies would be useful for farmers to improve the agricultural production in the region and influence the government policy for the application of paper mill wastes in agricultural industry.